130x1g2 - CCSDS

TM SYNCHRONIZATION AND CHANNEL CODING—SUMMARY OF CONCEPT AND RATIONALE2 OVERVIEW OF CCSDS TELEMETRY SYSTEM2.1 INTRODUCTIONThe purpose of a telemetry system is to reliably and transparently convey measurementinformation from a remotely located data generating source to users located in space or onEarth. Typically, data generators are scientific sensors, science housekeeping sensors,engineering sensors and other subsystems on-board a spacecraft.The advent of capable microprocessor based hardware will result in data systems withdemands for greater throughput and a requirement for corresponding increases in spacecraftautonomy and mission complexity. These facts, along with the current technical andadministrative environments, create a need for greater telemetering capability and efficiencywith reduced costs.In the past, most of the telemetry resources used by a science mission have been whollycontained within a cognizant Project office and, with the exception of the tracking network,are completely dedicated to that mission. The lack of effective standardization among variousmissions forces the ‘multi-mission’ tracking network to implement the lowest level oftelemetry transport service, i.e., bit transport. Higher level data delivery services, orientedmore toward computer-to-computer transfers and typical of modern day commercial andmilitary networks, have to be custom designed and implemented on a mission-to-missionbasis.The intent of the CCSDS Telemetry System is not only to ease the transition toward greaterautomation within individual space agencies, but also to ensure harmony among theagencies, thereby resulting in greater cross-support opportunities and services.The CCSDS Telemetry System is broken down into two major conceptual categories: a ‘TMSpace Data Link Protocol’ concept (references [2] and [7]) and a ‘TM Synchronization andChannel Coding’ concept (reference [3]).a) TM Space Data Link Protocol is a concept which facilitates the transfer of spaceacquireddata from source to user in a standardized and highly automated manner.TM Space Data Link Protocol provides a mechanism for implementing common datastructures and protocols which can enhance the development and operation of spacemission systems. TM Space Data Link Protocol addresses the following twoprocesses:1) The end-to-end transport of space mission data sets from source applicationprocesses located in space to distributed user application processes located inspace or on Earth.2) The intermediate transfer of these data sets through space data networks; morespecifically, those elements which contain spacecraft, radio links, trackingstations and mission control centers as some of their components.CCSDS 130.1-G-2 Page 2-1 November 2012